Pneumatic Powered Surgical Stapling Device

ABSTRACT

A surgical stapler which includes or onto which a tool assembly can be mounted for deforming a plurality of surgical fasteners through and fastening tissue includes a housing having a fixed handle and a clamping handle mountable to the housing. The clamping handle is selectively movable relative to the fixed handle from a first position in spaced relation relative to the fixed handle to a second position closer to the fixed handle to actuate the clamping of tissue. An adapter yoke is included which translates within the housing upon actuation of the clamping handle. The adapter yoke mechanically cooperates with a lead screw to actuate the tool assembly to clamp tissue. A drive assembly is also included for rotating a shaft which mechanically engages the lead screw. Upon selective activation of the drive assembly, the shaft rotates the lead screw to advance a roll nut and force a firing piston into the tool assembly to deform the surgical fasteners through and fasten the tissue.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from of U.S. Provisional ApplicationSer. No. 60/416,094 filed on Oct. 4, 2002 by Philip C. Roy entitled“PNEUMATIC SURGICAL STAPLING DEVICE”, and incorporates its entirecontents by reference herein.

BACKGROUND

1. Technical Field

The present disclosure relates to surgical staplers for implantingmechanical surgical fasteners into the tissue of a patient, and, inparticular, to surgical staplers which are pneumatically powered to firesurgical fasteners into tissue.

2. Background of Related Art

Surgical staplers which implant surgical fasteners into tissue using theforce of pressurized gas are known in the art. The majority of theseinstruments utilize a pressurized air supply which connects to a triggermechanism by way of an intricate series of hoses and actuators. Thetrigger mechanism, when depressed, simply releases pressurized gas toimplant a fastener into tissue.

Current known devices can typically require 10-60 pounds of manual handforce to clamp tissue and deform surgical fasteners through tissuewhich, over repeated use, can cause fatigue.

It would be desirable to provide a low cost pneumatic motor orreciprocator which couples to a pressurized gas supply (disposed eitherinternally or externally relative to the surgical stapler) and providesthe needed energy required to fire the instrument to form a series ofsurgical fasteners into and through tissue. It would also be desirableto provide an ergonomically advanced surgical stapler which reducesfatigue during repeated use and provides the surgeon with more tactilefeedback during activation of the stapler.

SUMMARY

The present disclosure relates to a surgical stapler having a distal endonto which a tool assembly having a pair of opposing tissue engagingsurfaces can be mounted for deforming a plurality of surgical fastenersthrough tissue to fasten tissue. The stapler includes a housing having afixed handle which extends therefrom. A clamping handle is mounted tothe housing and selectively movable relative to the fixed handle from afirst position in spaced relation relative to the fixed handle to asecond position closer to the fixed handle to actuate the clamping oftissue. Advantageously, an adapter yoke is included which translateswithin the housing upon actuation of the clamping handle. The adapteryoke mechanically cooperates with a lead screw to actuate the toolassembly to clamp tissue. The stapler also includes a drive assemblyhaving a shaft which is mechanically engaged with the lead screw. Uponselective activation of the drive assembly, the shaft rotates the leadscrew to advance a roll nut distally along the lead screw to force afiring piston into the tool assembly when mounted on the housing todeform the surgical fasteners through the tissue to fasten the tissue.

Preferably, the drive assembly is pneumatically powered and includes apressure sensitive trigger which is selectively variable to regulate theadvancement of the roll nut along the lead screw which, in turn,regulates the speed at which the surgical fasteners are deformed.Advantageously, the stapler includes at least one safety which preventsactivation of the drive assembly until the safety is deactivated. In oneembodiment according to the present disclosure, the safety isautomatically deactivated when the clamping handle is moved to thesecond position to clamp tissue. Preferably, one of the safeties is afiring safety which prevents the roll nut from advancing to force thefiring piston until the firing safety is deactivated.

In another embodiment according to the present disclosure, the shaftrotates upon activation of the drive assembly which in turn rotates thelead screw. Preferably, the stapler includes a switch for reversing therotation of the shaft of the drive assembly upon activation thereof.

The present disclosure also relates to a stapler having a housing withan elongated member attached thereto and a tool assembly which isattached to the distal end of the elongated member. The tool assemblyincludes opposing tissue engaging surfaces and a plurality of surgicalfasteners. The stapler also includes a selectively activateable driveassembly having an actuation shaft which is mechanically engaged with alead screw. Upon selective activation of the drive assembly, theactuation shaft rotates the lead screw to advance a firing shaft andactuate the tool assembly to initially clamp tissue between opposingtissue engaging surfaces of the tool assembly and subsequently to forcea firing piston into the tool assembly to deform the surgical fastenersthrough tissue to fasten tissue.

In one embodiment of the present disclosure, the actuation shaftreciprocates upon activation of the drive assembly. The actuation shaft,in turn, is mechanically engaged with a converter which converts thereciprocal motion of the actuation shaft into rotary motion of the leadscrew.

In yet another embodiment according to the present disclosure, thestapler includes a canister for containing a supply of pressurized gasfor activation of the drive assembly. Preferably, the canister isinternally disposed within the housing. Advantageously, the canister isselectively replaceable.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the subject instrument are described herein withreference to the drawings wherein:

FIG. 1A is a schematic, side view with portions broken away of asurgical stapler according to the present disclosure having apneumatically-powered rotary drive assembly for forming fasteners;

FIG. 1B is a schematic, side view with portions broken away of analternate embodiment of a tool assembly for use with the stapler of FIG.1A;

FIG. 2 is a schematic, side view with portions broken away of analternate embodiment of the pneumatically-powered surgical stapleraccording to the present disclosure having a reusable canisterexternally attached thereto;

FIG. 3 is a schematic, side view with portions broken away of a surgicalstapler according to the present disclosure having apneumatically-powered reciprocating drive assembly for formingfasteners;

FIG. 4 is a schematic, side view with portions broken away of a surgicalstapler according to the present disclosure having apneumatically-powered reciprocating drive assembly for forming fastenersand an internally-disposed canister;

FIG. 5A is side, perspective view removed and portions broken away ofanother embodiment according to the present disclosure showing a manualclamping handle for clamping tissue in a pre-clamped position and apneumatic trigger shown disengaged from a safety valve for firing thestapler;

FIG. 5B is a side, perspective view of the embodiment of FIG. 5A whichshows the clamping handle in a clamped position and the pneumatictrigger in an engaged position with the safety valve for activating thepneumatic motor to fire fasteners; and

FIG. 6 is a schematic, exploded view of an adapter yoke which connectsto the drive assembly.

DETAILED DESCRIPTION

Referring initially to the embodiment disclosed in FIGS. 1A and 1B, asurgical stapler 10 is shown having a pneumatically-powered rotary driveassembly here shown as including a pneumatic motor 20. It is envisionedthat the presently disclosed drive assembly 20 can be utilized with anytype of known surgical stapler. As such, a general surgical stapler 10is schematically depicted in the drawings and described herein. Forexample, stapler 10 includes a housing 12 having an elongated member orshaft 30 attached thereto. Shaft 30 includes a proximal end 32 whichattaches to a distal end 21 of the housing 12 and a distal end 34 whichoperatively couples to a tool assembly or end effector 100. Toolassembly 100 depicted in FIG. 1A is a conventional longitudinal staplerhaving opposing tissue contacting surfaces 110 and 120 and tool assembly200 depicted in FIG. 1B is that of a conventional circular stapler (notshown) having opposing tissue contacting surfaces 210 and 220. For thepurposes herein, stapler 10 will be described as having tool assembly100 attached to distal end 34 thereof.

Housing 12 includes a fixed handle 65 which is generally formed like apistol grip to enhance manipulation of the stapler 10 as needed duringsurgery. Stapler 10 may also include a movable handle actuator 60 (shownin phantom) which is movable relative to fixed handle 65 (in thedirection of arrow “A”) to actuate opposing tissue contacting surfaces110 and 120 of tool assembly 100 (See arrow “B”) to manipulate, graspfasten and cut tissue. The proximal end of shaft 30 is integrallyassociated with or selectively attachable to housing 12, handle 65 orone or more actuating assemblies (not shown) of a manual (or other,e.g., robotic or computer operated) open or endoscopic surgical stapler1 (or system—not shown). Many types of mechanical actuators and handlemechanisms are known which are configurable to communicate with andactuate the functions of tool assembly 100.

As best seen in FIG. 1A, a staple deformation or staple firing mechanism70 and knife assembly 75 may also be included in distal end 34 of theshaft 30 and/or included with tool assembly 100. It is contemplated thatthe same or additional actuating mechanisms may be employed to drivestaple firing mechanism 70 and knife assembly 75. For example, FIGS. 5Aand 5B show one embodiment of a surgical stapler 510 which includes aclamping handle 560 which cooperates with tool assembly 100 to grasptissue while a separate motor drives staple firing mechanism 70 andknife assembly 75 through tissue.

FIG. 1A shows one embodiment of a stapler 10 which includes a simple,low cost rotary pneumatic drive assembly 20 housed within surgicalstapler 10 to actuate a firing shaft 55 which, in turn, cooperates withtool assembly 100 to clamp tissue between tissue engaging surfaces 110and 120 and to drive a plurality of surgical fasteners 350 throughtissue. Surgical stapler 10 is preferably, as shown, designed forone-handed operation by the user and requires minimal trigger force todeform the surgical fasteners 350 through tissue. In other words,stapler 10 is designed such that pneumatic drive assembly 20 actuatesand controls the high-force portion of the activation sequence (i.e.,the so-called “firing stroke”) thus alleviating user fatigue andallowing simple, consistent and repeated use of the stapler duringsurgery.

Actuation of pneumatic drive assembly 20 rotates a motor shaft 22 which,in turn, translates a firing shaft 55 which initially closes opposingtissue contacting surfaces 110 and 120 and subsequently forces staplefiring mechanism 70 and knife assembly 75 through tissue to sequentiallyfasten and separate the tissue. It is envisioned that pneumatic driveassembly 20 may cooperate with a clamping handle 60 which clamps tissuebetween surfaces 110 and 120 while pneumatic drive assembly 20 operatesto drive firing shaft 55. A series of gears, shafts, screws or othermechanisms may be employed to convert the rotational pneumatic energyfrom pneumatic drive assembly 20 to firing shaft 55 to actuate toolassembly 100. Air or other pressurized gas is preferably externallysupplied, e.g., through a pneumatic air hose 68, 68 a, from a hospital'sexisting pneumatic air or gas supply 300, e.g., pressurized gas outlet,to run pneumatic drive assembly 20. Alternatively, as shown in FIG. 4, aself-contained or rechargeable gas supply 405 may be disposed in thesurgical stapler 10 and be operatively connected to activate pneumaticdrive assembly 20.

Preferably, stapler 10 also includes a trigger, here, a movable pressuretrigger 80, which activates the supply of pressurized gas to firestapler 10. It is envisioned that trigger 80 may include a regulator 90which controls the amount of pressurized gas to pneumatic drive assembly20 to fire shaft 55. As such, by selectively squeezing trigger 80, theuser can control the initial grasping of the tissue with the opposingtissue contacting surfaces 110, 120 of tool assembly 100 andsubsequently control the firing force of stapler 10 through the tissue.The further, faster or harder that trigger 80 is squeezed, the fasterpneumatic drive assembly 20 turns, thus making stapler 10 fire morequickly and/or making the stapler fire with more power. Moreover, it iscontemplated that trigger 80 may include a series of graduations,incremental stops or a ratchet mechanism (not shown) to regulate thepressure of the gas being supplied to drive assembly 20 based on thedistance trigger 80 is depressed. A separate stop or switch (not shown)may also be included with the trigger 80 to switch the motor from a“grasping” mode to a “firing” mode. It is also envisioned that releasingtrigger 80 stops the supply of pressure to the pneumatic drive assembly20 and stops the firing stroke of stapler 10. As such, the stroke may bestopped at any time during initial grasping of the tissue or duringdeformation of the fasteners 350.

It is envisioned that pneumatic drive assembly 20 may also bereversible, i.e., retract the firing shaft 55 as needed and open thetissue contacting surfaces 110, 120 of tool assembly 100. Thus,directional switch 50 may be included with the pneumatic drive assembly20 to accomplish this purpose. In FIG. 1A, direction “A” indicatesforward and direction “B” indicates reverse.

FIG. 2 shows an alternate embodiment of a surgical stapler, 210, thatincludes an externally mounted air canister 250 which is removablyattached to stapler 210. Preferably, canister 250 is selectivelyreplaceable (or reusable) and supplies pressurized gas to operate aninternally disposed pneumatic drive assembly 220 to turn shaft 222. Itis envisioned that one of a series of different canisters 250 may beselectively attached to stapler 210 depending upon the type of tissuebeing fastened and the desired pressure range needed to properly fastenthe tissue. Canister 250 may also be internally disposed within fixedhandle 265 as shown in FIG. 4. Different canisters 250 may be sold as akit and color coded for specific tissue types or size/contents. Muchlike stapler 10 disclosed in FIG. 1, surgical stapler 210 may alsoinclude any one or any combination of structures or operating componentsdescribed above, e.g., housing 212, movable handle 80, switch 50,variable pressure trigger 280, trigger regulator 90, firing shaft, 55staple formation mechanism 70, knife assembly 75 and/or tool assembly100, 200. The distal end of shaft 30 can be operatively attached to atool assembly (not shown).

FIG. 3 shows another embodiment of the present disclosure, a surgicalstapler 310 which has a reciprocating pneumatic drive assembly orreciprocating motor 320 (i.e., reciprocating cylinder) coupled to apneumatic gas supply 300 to actuate firing shaft 355. More particularly,pneumatic air supply 300 may be attached to housing 312 and internallycoupled to a valve 305 which regulates the reciprocating speed of a pairof pistons 322 and 324 disposed within reciprocating drive assembly 320.An output shaft 328 from drive assembly 320 connects to a converter 345which is employed to convert the reciprocating energy from thereciprocating drive assembly 320 to actuate (i.e., translate) firingshaft 355. It is envisioned that a series of gears (not shown) may beutilized to accomplish this purpose. Stapler 310 may also include anyone or any combination of the operating components described above withrespect to FIG. 1, e.g., movable handle 60, switch 50, trigger 80,trigger regulator 90, staple formation mechanism 70, knife assembly 75and/or tool assembly 100, 200. The distal end of shaft 330 can beoperatively attached to a tool assembly (not shown).

It is envisioned that one of the many advantages of this disclosure overconventional surgical fasteners is that the amount of effort required tofire stapler 10, 210, 310 is nominal. This is primarily becausepneumatically driven motor 20, 220 or 320 does the majority of the workto fire the stapler 10, 210 or 310. Moreover, the unique combination ofa manual clamp-up and a motorized firing and retraction stroke will alsoreduce user fatigue and gives the user additional positive tactilefeedback during the clamping and firing strokes.

While other non-manually actuated staplers require either batteries oran external electrical power supply to assist in firing, the presentlydisclosed instrument utilizes an air supply 300 readily available inmost operating rooms by simple connection thereto. Thepresently-disclosed staplers 10, 210, 310 also allows the surgeon a widerange of firing possibilities from a “slow-fire” clamping and firingstroke to a “rapid-fire” clamping and firing stroke.

As mentioned above with respect to FIG. 2, it is envisioned that analternate embodiment of the stapler 410 (FIG. 4) may include aninternally or externally mounted canister 405 which is either sold as anintegral part of the stapler (for disposable staplers) or which isremovably attachable to the stapler 10 (for use with a reusable orreposable stapling instrument). As shown in FIG. 4, canister 405 isselectively replaceable or rechargeable and supplies pressurized gas tooperate the internal reciprocating drive assembly 420 disposed withinthe housing 412. It is envisioned that one of a series of canisters 405may be selectively attachable to the stapler 410 depending upon the typeof tissue being fastened and the desired pressure range needed toproperly fasten the tissue. Canister 405 may be removably engaged withinhousing 412 and mechanically (or electro-mechanically) coupled to avalve 408 which regulates the reciprocating speed of pistons 422 and 424disposed within the reciprocating drive assembly 420. A user canselectively regulate the reciprocating speed of firing shaft 455 bycontrolling the distance trigger 480 is depressed. Much like theembodiment described with respect to FIG. 3, a converter 445 may beemployed to convert the reciprocating energy from the reciprocatingmotor 420 to actuate (i.e., translate) the firing shaft 455. Again, thisstapler 410 may also include any one or any combination of operatingcomponents described above with respect to FIG. 1, e.g., movable handle60, switch 50, trigger regulator 90, staple formation mechanism 70,knife assembly 75 and/or tool assembly 100, 200.

FIGS. 5A and 5B show an alternate surgical stapler 510 according to thepresent disclosure. Stapler 510 includes a manual clamping handle 560for use with the pneumatic drive assembly 520. More particularly, muchlike the aforedescribed staplers 10, 210, 310 and 410, stapler 510includes a housing 512 which contains a pneumatic drive assembly 520which drives a firing shaft 555 to deform the plurality of surgicalfasteners (not shown) when tissue is disposed between the opposingtissue contacting surfaces 110 and 120 (FIG. 1A) of tool assembly 100.Stapler 510 also includes a trigger 580 which activates the supply ofpressurize gas to drive pneumatic drive assembly 520 to fire stapler510.

Preferably, firing shaft 555 of stapler 510 is designed as a lead screwwhich is connected to pneumatic drive assembly 520 via an adapter yoke595. A screw roll nut 575 threadably engages lead screw 555 such thatrotary movement of lead screw 555 translates into linear movement ofroll nut 575 which advances a firing piston 578. Firing piston 578cooperates with a tool assembly, e.g., tool assembly 100 or 200, to fireand deform fasteners (not shown) through tissue disposed betweenopposing tissue contacting surfaces 110 and 120 of tool assembly 100. Asmentioned above, either tool assembly 100 or 200 (or another differenttype of suitable tool assembly) may be designed to cooperate with firingshaft 555 to drive fasteners through tissue.

As best shown in FIG. 5A, manual clamping handle 560 is mounted tohousing 512 about a pivot 562 which allows the user to selectively movehandle 560 relative to fixed handle 565. Handle 560 includes a grip area561 defined therethrough which is designed to accept a user's fingers tofacilitate actuation of handle 560 from a pre-clamp position whereinhandle 560 is most spaced from fixed handle 565 to a series ofsubsequent positions wherein handle 560 is positioned adjacent fixedhandle 565. Handle 560 also includes an upper or working end 563 whichis preferably bifurcated into flanges 564 a and 564 b. Flanges 564 a and564 b, in turn, define a slot 567 therein which is dimensioned toreceive the adapter yoke 595. Flanges 564 a and 564 b include one ormore cut outs or notches 566 defined therein which are designed tocooperate with a corresponding number of pins 596 which extend fromadapter yoke 595. It is envisioned that the pins 596 and notches 566enhance mechanical engagement of the adapter yoke 595 and flanges 564 aand 564 b to promote consistent operation of tool assembly 100 uponactuation of handle 560. Pressurized air or gas is externally suppliedfrom a hospital's existing pneumatic air or gas supply through one ormore pneumatic air hoses 300 attached to the proximal end of the stapler510. As mentioned above with respect to FIG. 4, a self-contained orrechargeable gas supply (not shown) may be disposed in the surgicalstapler 510 and be operatively connected to activate drive assembly 520.

As best seen in FIGS. 5A and 5B, upon actuation of handle 560, adapteryoke 595 engages a proximal end 556 of lead screw 555 such thattranslational movement of adapter yoke 595 forces lead screw 555 throughroll nut 575 to move the opposing surfaces 110 and 120 of tool assembly100 from a first position wherein the opposing surfaces 110 and 120 arespaced relative to one another to a second position wherein the opposingsurfaces 110 and 120 cooperate to grasp tissue therebetween. FIG. 5Bshows the relative movement of handle 560 and the corresponding movementof adapter yoke 595 and lead screw 555 upon actuation of handle 560.

FIG. 6 shows a schematic representation of adapter yoke 595 of FIG. 5Aand 5B which cooperates with the clamping handle 560 to translate (Seearrow “D”) lead screw 555 to clamp tissue as described above. Moreparticularly, adapter yoke 595 includes a collar 598 which mechanicallyengages shaft 521 of the pneumatic drive assembly 520. Rotation of shaft521 correspondingly rotates a cylinder 597 disposed within collar 598which, in turn, rotates lead screw 555. Preferably, shaft 521 is keyedto securely fasten within a corresponding dual slot 599 defined incylinder 597 to insure positive engagement of shaft 521 with cylinder597 and to permit rotary movement in either direction as shown by arrow“E”.

In operation, as the user actuates handle 560, adapter yoke 595translates to force lead screw 555 through roll nut 575 which, in turn,closes the opposing surfaces 110, 120 of tool assembly 100 about tissuegrasped therebetween. Roll nut 575 is held fast by a safety 576(described below) which allows screw 555 to rotate through roll nut 575and actuate tool assembly 100. This is known as the “clamping stroke”.Adapter yoke 595 allows screw 555 to rotate therewithin, but relativelinear translation between adapter yoke 595 and screw 555 remains fixed.It is envisioned that the clamping stroke may be incrementally actuatedvia a ratchet or other mechanism (not shown) to allow the user to slowlyor incrementally grasp tissue between opposing surfaces 110 and 120 oftool assembly 100. This also enables the user to maintain tool assembly100 in a fully actuated and clamped position about the tissue during theso-called “firing stroke”.

When clamping handle 560 is fully actuated, trigger 580 is positionedfor activation of pneumatic drive assembly 520 which fires surgicalfasteners into the tissue. Preferably, stapler 510 is designed such thatin order to activate the pneumatic drive assembly 520 to fire surgicalfasteners, the clamping stroke must be fully completed, i.e., handle 560must be fully actuated. As best shown in the comparison of FIGS. 5A and5B, once handle 560 is fully actuated, trigger 580 is positioned to abutagainst a trigger safety 582 mechanically associated with trigger valve590. Activation of trigger 580 automatically depresses safety 582 andopens trigger valve 590 which activates drive assembly 520. It isenvisioned that if handle 560 is not fully actuated (i.e., the clampingstroke is not completed), safety 582 will remain activated. It is onlywhen handle 560 is fully actuated that safety 582 releases to allowactivation of the firing stroke.

In addition and prior to initiating the firing stroke, a second safety576 may be provided and need to be actuated (i.e., manually depressed orotherwise actuated) to disengage or release roll nut 575 from a fixedorientation to allow pneumatic drive assembly 520 to rotate lead screw555 and fire piston 578 to deform surgical fasteners (See FIG. 5B). Itis envisioned that safety 582 and 576 may be one in the same or safeties582 and 576 may be designed to mechanically (or electro-mechanically)cooperate with one another to control the firing stroke.

It is envisioned that trigger valve 590 regulates the speed of driveassembly 520 which, as can be appreciated, gives the user additionalcontrol over the formation of fasteners. For example, the speed of thedeformation of surgical fasteners can be selectively controlled by theuser, e.g., “slow-fire” or “rapid fire”, as well as the retraction speedof firing piston 578. As can be appreciated this gives the surgeonadditional tactile control during the firing stroke. Moreover, it isenvisioned that trigger 580 and trigger valve 590 maybe configured suchthat releasing trigger 580 will instantly stop firing piston 578 andmaintain firing piston 578 in linear position relative to instrumentshaft 530 for subsequent re-activation. Again, these configurationsenhance tactile control over the firing stroke.

As mentioned above, after the clamping stroke is completed (and thesafety mechanism(s) 576 (and 582, if applicable) have been deactivated),the user squeezes trigger 580 to translate firing piston 578 and deformthe surgical fasteners. More particularly, trigger 580 cooperates withtrigger valve 590 to regulate the pneumatic pressure to the pneumaticdrive assembly 520 which, in turn, regulates the speed of shaft 521. Thespeed of the rotation of shaft 521 is directly related to the speed atwhich lead screw 555 rotates to cause linear reciprocation of roll nut575. As described above, trigger 580 may be incrementally activatablefrom a fully open position allowing full pneumatic pressure (i.e.,maximum firing speed) to fully closed position (i.e., stop) thusproviding additional tactile control over the firing sequence.Preferably, a variable speed, pressure sensitive trigger 580 is utilizedto activate the pneumatic drive assembly 520 to drive roll nut 575 andadvance and retract firing piston 578.

Roll nut 575, in turn, translates along lead screw 555 forcing firingpiston 578 to deform the surgical fasteners (not shown). The driveassembly 520 continues to turn lead screw 555 to translate roll nut 575the appropriate linear distance to complete the deformation of surgicalfastener(s). It is envisioned that once the appropriate distance hasbeen traveled and surgical fasteners are completely formed through thetissue, drive assembly 520 automatically stops signaling the user toswitch drive assembly 520 to reverse and retract roll nut 575 proximallyon lead screw 555. Alternatively, drive assembly 520 may automaticallyshift into reverse and begin retraction of roll nut 575. It iscontemplated that the roll nut 575 and lead screw 555 configurationprovides a simple, low friction energy conversion from rotary motion tolinear motion. Drive assembly 520 may also be configured to stop onceretraction of roll nut 575 has completed.

It is contemplated that roll nut 575, upon retraction, will reset backto relatively the same position as after manual clamping. Safety 576 maythen re-activated (either automatically or manually) to lock roll nut575 in a fixed orientation to allow re-actuation or release of manualclamping handle 560 and linear retraction of lead screw 555 which opensthe opposing tissue contacting surfaces 110 and 120 of tool assembly 100to release the tissue. At this point and with a reusable stapler 10, anew cartridge or single use loading unit (SULU) may be loaded and thestapler reused.

As explained above with reference to the embodiment of FIG. 1A, stapler510 may include a 2-position switch (not shown) which controls the driveassembly 520 to allow the user to selectively advance and retract firingpiston 578 as needed during surgery.

From the foregoing and with reference to the various drawings, thoseskilled in the art will appreciate that certain modifications can bemade to the present disclosure without departing from the scope of thesame. For example, the clamping handle may include a locking mechanism(not shown) which locks the handle relative to the fixed handle uponcompletion of the clamping stroke.

Although the presently disclosed staplers utilize a pneumatic driveassembly to drive the firing piston, it is envisioned that an electricdrive assembly (not shown) may also be utilized to accomplish the samepurpose. As such, similar trigger assemblies, switches and safetymechanisms may be employed to cooperate with the electric drive assemblyto advance and retract the firing piston to deform the surgicalfasteners.

Preferably, the presently disclosed staplers are designed for endoscopicuse and are dimensioned to fit through a trocar or cannula for variousendoscopic and laparoscopic procedures. As can be appreciated, theoverall dimensions of the tool assembly and the elongated shaft aresized accordingly to fit through the trocar or cannula. Alternatively,the presently disclosed staplers may also be designed and/or used foropen surgical procedures. The enclosed surgical staplers preferably aresuitable for one-handed operation by the user.

It will be understood that various modifications may be made to theembodiments shown herein. Therefore, the above description should not beconstrued as limiting, but merely as exemplifications of preferredembodiments. Those skilled in the art will envision other modificationswithin the scope and spirit of the claims appended hereto.

1. A surgical stapler having a distal end onto which a tool assemblyhaving a pair of opposing tissue engaging surfaces can be mounted fordeforming a plurality of surgical fasteners through and fasten tissue,the surgical stapler comprising: a housing having a fixed handle; aclamping handle mounted to said housing and selectively movable relativeto said fixed handle from a first position in spaced relation relativeto said fixed handle to a second position closer to said fixed handle toactuate the clamping of tissue; an adapter yoke which translates withinsaid housing upon actuation of said clamping handle, said adapter yokemechanically cooperating with a lead screw to actuate the tool assemblyto clamp tissue; a drive assembly including a shaft, said shaft beingmechanically engaged with said lead screw such that upon selectiveactivation of said drive assembly, said shaft rotates said lead screw toadvance a roll nut distally along said lead screw to force a firingpiston into a tool assembly when mounted on the housing to deform thesurgical fasteners through and fastening the tissue.
 2. A surgicalstapler according to claim 1, wherein said drive assembly ispneumatically powered.
 3. A surgical stapler according to any precedingclaim, wherein said drive assembly is selectively variable to regulatethe advancement of said roll nut along said lead screw which, in turn,regulates the speed at which said surgical fasteners are deformed.
 4. Asurgical stapler according to any preceding claim, wherein said staplerfurther comprises a pressure sensitive trigger which regulates theadvancement of said roll nut along said lead screw which, in turn,regulates the speed at which said surgical fasteners are deformed.
 5. Asurgical stapler according to any preceding claim, wherein said staplerincludes at least one safety which prevents activation of said driveassembly until said safety is deactivated.
 6. A surgical stapleraccording to any preceding claim, wherein said at least one safety isautomatically deactivated when said clamping handle is moved to saidsecond position to clamp tissue.
 7. A surgical stapler according to anypreceding claim, wherein said roll nut includes a firing safety whichprevents said roll nut from advancing to force said firing piston untilsaid firing safety is deactivated.
 8. A surgical stapler according toany preceding claim, wherein said stapler includes a switch forreversing the rotation of said shaft of said drive assembly uponactivation thereof.
 9. A surgical stapler according to any precedingclaim, wherein said shaft rotates upon activation of said drive assemblywhich in turn rotates said lead screw.
 10. A surgical stapler,comprising: a housing; an elongated member attached to the housing; atool assembly attachable to the distal end of the elongated member, saidtool assembly including an anvil assembly and a cartridge assembly eachhaving an opposing tissue engaging surface, said cartridge assemblyincluding a plurality of surgical fasteners; a selectively activateabledrive assembly including an actuation shaft, said actuation shaft beingmechanically engaged with a lead screw such that upon selectiveactivation of said drive assembly, said actuation shaft rotates saidlead screw to advance a firing shaft and actuate said tool assembly toinitially clamp tissue between opposing tissue engaging surfaces of saidtool assembly and subsequently to force a firing piston into said toolassembly to deform the surgical fasteners through and fasten tissue. 11.A surgical stapler according to claim 10, wherein said actuation shaftreciprocates upon activation of said drive assembly, said actuationshaft being mechanically engaged with a converter which converts thereciprocal motion of said actuation shaft into rotary motion of saidlead screw.
 12. A surgical stapler according to claim 10, wherein saidactuation shaft rotates upon activation of said drive assembly which inturn rotates said lead screw.
 13. A surgical stapler according to claim10, 11 or 12, wherein said stapler further comprises a pressuresensitive trigger which regulates the speed of drive assembly which, inturn, regulates the speed at which said surgical fasteners are deformed.14. A surgical stapler according to claim 10, 11, 12 or 13, wherein saidstapler further comprises a switch for reversing the rotation of saidshaft of said drive assembly upon activation thereof.
 15. A surgicalstapler according to any preceding claim, wherein said stapler furthercomprises a canister for containing a supply of pressurized gas foractivation of said drive assembly, said canister being internallydisposed within said housing.
 16. A surgical stapler according to anypreceding claim, wherein said canister is selectively replaceable.
 17. Asurgical stapler according to any preceding claim, wherein saidelongated member and said tool assembly are configured for endoscopicuse.
 18. A surgical stapler according to any preceding claim, whereinthe surgical stapler is suitable for one-handed operation.